Policy engines are used in communication networks to enforce operator defined policies as may be related to gating control, Quality of Service (QoS) control, QoS signaling etc. Examples of such policy engines are the Policy Charging and Rules Function (PCRF) in mobile networks as defined by the 3rd generation partnership program (3GPP), the Serving Policy Decision Function (SPDF) in fixed networks and the Packet Cable Policy Server in cable networks.
In communication networks, it is desirable that a plurality of policy engines is deployed. When a plurality of policy engines are present in a communication network, discovery procedures for policy engines are needed to direct requests from network elements to policy engines. Such discovery procedures should also ensure that requests from various network elements are directed the same policy engine throughout a session.
One solution to efficiently perform the discovery procedure is to deploy a policy request router, such as a Diameter Routing Agent (DRA) defined by the 3GPP. The policy request router is a functional element that ensures that all policy related messages in a session of a certain subscriber reach the same policy engine when multiple and separately addressable policy engines have been deployed. The policy request router maintains the policy engine routing information during the session and removes such information once the session is terminated.
Policy engines can control policies for a group subscription which may comprise a plurality of subscribers. If policy related requests for sessions of different subscribers within a group are directed to different policy engines, policies related to group subscription cannot be enforced efficiently, since data inconsistencies may occur and it may necessitate additional signaling in order to avoid the data inconsistencies. These problems may arise because subscription, provisioning and/or usage related information for the group may be cached differently in the different policy engines.